A longitudinal study of iris parameters and their relationships with temperament characteristics

Introduction: A previous study suggested that iris parameters may be related to temperament and because they are innate and are unchangeable over time. This longitudinal study examined the robustness of iris parameters, temperament characteristics (TC), and their relationship over a 1 year period. Methods: A total of 70 healthy subjects who participated in the 2013 study were interviewed 1 year later. They were asked to complete the Korean version of the Temperament and Character Inventory (TCI), and 6 iris parameters (iris density, pigment, nerve ring, toxic radii, pupil area ratio [PAR], and autonomic nerve wreath area ratio [ANWAR]) were calculated. Subsequently, intra-and inter-rater reliabilities and robustness of the iris parameters were examined using an intra-class coefficient (ICC), and the relationships between the iris parameters and TC scores in 2014 were compared with those recorded in 2013. Finally, decision tree modeling was conducted to examine which iris parameters were related to TC. Results: The 6 iris parameters possessed excellent levels of reliability and robustness, ranging from 0.797 to 1.000 of ICCs. Among the 5 significant relationships between iris parameters wereTC scores, iris density and harm avoidance, pigment and reward dependence, ANWAR and persistence had the same significant relationships to those in 2013. Decision tree modeling showed that PAR, iris density, ANWAR, and toxic radii were related to individual TCs (classification accuracy: 77.5-88.9%). Conclusions: Iris parameters and the relationships between iris parameters and TC are robust. Iris parameters may serve as a contributing factor to one's TC. (C) 2016 Elsevier GmbH. All rights reserved.